The size and thickness of portable wireless communication apparatuses, such as mobile phones, have been rapidly reduced. Portable wireless communication apparatuses have been transformed from apparatuses to be used only as conventional telephones, to data terminals for transmitting and receiving electronic mails and for browsing web pages of WWW (World Wide Web), etc. Further, since the amount of information to be handled has increased from that of conventional audio and text information to that of pictures and videos, a further improvement in communication quality is required. In addition, portable wireless communication apparatuses are required to handle various applications, including telephone call for voices, data communication for browsing web pages, watching of television broadcasts, etc. In such circumstances, an antenna apparatus operable over a wide frequency range is required for wireless communications of the respective applications.
As conventional antenna apparatuses capable of adjusting a resonant frequency while covering a wide frequency band, there are, e.g., an antenna apparatus of Patent Literature 1, in which an antenna element portion is provided with a slit to adjust a resonant frequency, and a notch antenna of Patent Literature 2, in which a slit is provided with a trap circuit.
The antenna apparatus of Patent Literature 1 is configured including a planar radiating element (radiating plate), and a ground plate facing the planar radiating element in parallel, and further including a feeding portion located at about the center of an edge of the radiating plate for supplying high-frequency signals, a short-circuiting portion for short-circuiting the radiating plate and the ground plate near the feeding portion, and two resonators formed by providing a slit in the edge of the radiating plate substantially opposed to the feeding portion. The degree of coupling between the two resonators is optimized by adjusting the shape or dimensions of the slit, or by loading a reactance element or conductor plate on the slit. Thus, a small and low-profile antenna can be obtained with suitable characteristics.
The notch antenna of Patent Literature 2 can open the slit at the position of the trap circuit for radio frequency signals when requiring resonance in a low frequency band for communication, and on the other hand, can close the slit at the position of the trap circuit for radio frequency signals when requiring resonance in a high frequency band for communication. Thus, the resonant length of the notch antenna can be appropriately changed according to the frequency band to resonate for communication.